The use of implants for a variety of prosthetic procedures is widely accepted in numerous fields. In some cases, diseased, damaged, or defective bone and/or tissue, such as malignant tumors, may require removal of the afflicted tissue and bone. Where the resection cavity is large, an implant may be inserted to occupy the space left by the removed tissue or bone. Some cases require the introduction of a permanent implant which remains in the resection cavity indefinitely. It is generally desirable that such an implant be of sufficient strength and biocompatibility to coexist and integrate with adjacent remaining tissue and bone. Implants for replacing bone are typically autografts, allografts, or ceramics such as calcium phosphate or calcium sulfate, or metals such as stainless steel or titanium.
The desired advantages of permanent implants can also lead to drawbacks. For instance, while many permanent implants are constructed of load-bearing materials, implants made of such materials may not react well to procedures such as radiation treatment. Metal implants may act as a “lens” during radiation treatment, effectively refocusing and intensifying radiation waves onto to a small location on the patient's or surgeon's body. Autografts require lengthy procedures (e.g. harvesting, shaping, and implantation) and thus time constraints may not allow their use.
Permanent autografts and allografts may react poorly to chemotherapy treatments. Chemotherapy aims to kill cancer cells, as they are normally weaker than surrounding healthy cells. However, typically the cells in autografts and allografts are of a somewhat weakened state when inserted in a resection cavity. Therefore, chemotherapy can have the adverse effect of destroying the autograft or allograft cells themselves, thereby weakening the permanent implant and rendering it less effective. Furthermore, if the patient has poor blood supply in the affected area, allografts and autografts may not be effective.
Thus, a temporary implant may be used to occupy a resection cavity left by the removal of the afflicted area of tissue and bone. A permanent implant (i.e. allograft or autograft) may eventually be used, but it may be desirable to conclude treatments such as radiation or chemotherapy before installing them. Temporary implants used in this manner may assist surgeons by maintaining the size of the resection cavity from the time of the first removal of bone and/or tissue to the time of the permanent implant introduction and placement. If the cavity were left unfilled during the chemotherapy or radiation therapy period, the soft tissue surrounding the site could intrude into the cavity left by the primary removal of bone and/or tissue, thereby interfering with subsequent installation of a permanent implant. Thus, a temporary implant would provide the advantage of resisting such soft tissue intrusion, while also providing a short term cosmetic replacement body to approximate the patient's original anatomy during the chemotherapy or radiation period.